Starch-amine-based polyether polyols and polyurethane foams prepared therefrom

ABSTRACT

A novel process for the preparation of starch-amine-based polyols which involves reacting starch with a polyhydric alcohol in the presence of an acid catalyst to form a crude polyglucoside reaction product, the proportion of alcohol to starch being at least 0.3 mole of alcohol per glucose unit weight of starch. An amine compound is admixed with the reaction product, and the mixture is then oxyalkylated with a lower alkylene oxide. Polyurethane foams may be prepared by reacting the resulting polyether polyols with an organic polyisocyanate in the presence of a foaming agent and a reaction catalyst. The physical properties of the resulting foams are excellent.

This is a division, of application Ser. No. 218,870, filed Dec. 22,1980, now U.S. Pat. No. 4,342,864.

This invention relates to a process for the preparation ofstarch-amine-based polyether polyols, to the product resulting from theprocess, and to the use of these polyols in the preparation ofpolyurethane foams.

Polyurethane foams have been used in the preparation of structuralpanels, insulation, cushions, pillows, mattresses, and the like.Generally these foams are prepared by reacting an organic polyisocyanatewith a polyol in the presence of a foaming agent and a catalyst.Extensive efforts have been made to reduce the cost of preparing thesefoams. Because of the low cost of starch, efforts have been made toemploy starch as a polyol reactant in the preparation of urethane foams.The use of starch directly has been unsatisfactory, however, because ofprocessing difficulties and the poor physical properties of the foamwhich results. Oxyalkylated starch yields satisfactory foams, but thedirect oxyalkylation of starch results in degradation or decompositionof the starch and a product which is not uniform in chemical or physicalproperties.

A satisfactory process for utilizing starch as a component in thepreparation of polyurethane foams is disclosed in U.S. Pat. No.3,277,213 issued to Stephen Fuzesi on Oct. 4, 1966. In this processstarch is added to a polyhydric alcohol containing at least two hydroxylgroups in a proportion equivalent to at least 0.3 mole of the alcoholper mole of glucose unit weight of starch in the presence of an acidcatalyst. The resulting mixture is then oxyalkylated to yield apolyether polyol suitable for use in preparing polyurethane foams.However, there is no disclosure in this patent of adding an aminecompound as a co-initiator to the mixture prior to oxyalkylation.

It is, therefore, a primary object of the present invention to provide anovel process for preparing a starch-amine-based polyether polyol.

It is a further object of the present invention to provide a novelstarch-amine-based product.

It is yet another object of the present invention to provide rigidpolyurethane foams having highly satisfactory physical properties byutilizing the novel starch-amine-based polyether polyols.

These and other objects of the invention will be apparent from thefollowing detailed description thereof.

It has now been discovered that the objects of the invention may beaccomplished by: reacting starch and a polyhydric alcohol in thepresence of an acid catalyst to form a crude polyglucoside reactionproduct, the proportion of alcohol to starch being at least 0.3 mole ofalcohol per glucose unit weight of starch; and admixing this crudeproduct with an amine, and oxyalkylating the mixture with an alkyleneoxide having from 2 to about 6 carbon atoms. The resulting polyetherpolyols may then be reacted with an organic polyisocyanate, a foamingagent and a catalyst to yield urethane foams having excellent physicalproperties.

The starch-amine-based polyether polyol of this invention may beprepared from any starch, i.e., any compound having the formula (C₆ H₁₀O₅)_(x). These compounds are carbohydrates or polysaccharides whichoccur naturally in many plant cells. Typical starches which may beconveniently employed include potato starch, corn starch, chlorinatedstarches, rice starch, tapioca starch, wheat starch, mixtures thereofand the like. From an economic standpoint, potato starch and corn starchare preferred.

Any polyhydric alcohol containing at least two hydroxyl groups may beemployed in the preparation of the starch-amine-based polyol of thisinvention It is preferred, however, to employ glycerol, ethylene glycol,diethylene glycol, propylene glycol, dipropylene glycol, sorbitol andthe like due to availability and ease of reaction. However, polyhydricalcohols which may be conveniently employed include, but are not limitedto, pentaerythritol, hexanetriol, trimethylol propane, trimethylolethane, 1,2-butanediol, triethylene glycol, 2-butene-1,4-diol,2-butyne-1,4-diol, 3-chloro-1,2-propanediol, 2-chloro-1,3-propanediol,mixtures thereof and the like.

The polyhydric alcohol is normally employed in an amount of at least 0.3mole of polyol per one glucose unit weight of starch. The upper limit ofpolyhydric alcohol is not critical; however, it is preferred to use from0.5 to 5 moles of alcohol per one glucose unit weight of starch in orderto retain as much as possible of the starch characteristic in theproduct.

Each glucose unit weight of starch is equivalent to 162 grams of starchon an anhydrous basis. Normally, each glucose unit weight of starchcontains water associated therewith. In a preferred embodiment of thepresent invention, a small amount of water, preferably not more thanabout 2 moles or 36 grams, per glucose unit weight of starch, is addedwith the starch. However, smaller or larger proportions of water may bepresent if desired.

The acid catalyst may be any inorganic or Lewis acid catalyst.Representative Lewis acid catalysts include, but are not limited to,boron trifluoride etherate, aluminum trichloride, ferric chloride,stannic chloride, titanium tetrachloride, etc., and mixtures thereof.Other suitable acid catalysts include inorganic acids such as sulfuricacid, phosphoric acid, hydrochloric acid, hydrofluoric acid, nitric acidand the like. The preferred catalysts are boron trifluoride etherate andsulfuric acid. The acid catalyst is employed in a catalytic proportionto catalyze the reaction between the starch and the polyhydric alcohol.The proportion of catalyst is generally in the range between about 0.5and about 5, and preferably between about 1 and about 3, percent of thecombined weight of the starch and polyhydric alcohol, but greater orlesser proportions may be utilized if desired.

The initial reaction between the starch and the polyhydric alcohol isaccelerated by employing elevated temperatures, i.e., preferably in therange between about 60° and about 200° C. The specific temperature ofthe reaction will vary depending on the degree of completion, reactantsemployed, time of reaction, and other reaction conditions. Similarly,the reaction time will vary depending upon the temperature of thereaction, reactants employed and the amounts thereof.

In a preferred procedure for carrying out the initial step of theprocess of the present invention, the starch is slowly added to a hotfluid mixture of the polyhydric alcohol and the acid catalyst which ismaintained at a temperature in the range of between about 100° and about200° C. After the starch has been added, the mixture is maintained atthis elevated temperature until the starch is completely dissolved inthe reaction mixture. Generally, at least about 30 minutes, and no morethan about 3 hours, are required.

While it is not desired to be bound by theory, it is believed that thestarch will degrade in the presence of the polyhydric alcohol and thecatalyst forming glucosides. The relative proportions of glucosidecompounds in the reaction product will vary depending upon the reactantproportions and the conditions employed in carrying out the reaction.

In the next step of the process of this invention, the crudepolyglucoside reaction product is admixed with an amine compound, theamine compound being employed in an amount of at least about 0.1 mole toabout 10 moles per glucose unit weight of starch. An oxyalkylationcatalyst is added; and then, while maintaining the temperature withinthe range of from about 60° to about 200° C., an alkylene oxide or amixture of alkylene oxides is introduced, using random or step-wiseaddition, into the mixture. The resultant oxyalkylated product is aco-oxyalkylated product in that the alkylene oxide reacts with theglucoside components of the crude reaction mixture and with the aminecompound.

Oxyalkylation may be conducted with or without separating any waterpresent. When the water is not removed, the water will be oxyalkylatedand will produce an oxyalkylated diol as a constituent of thestarch-amine-based polyether polyol.

In the process of the present invention, any suitable amine compound,including mixtures of compounds containing an amine, may be employed.Suitable amines include the following and mixtures thereof:

a. The primary aliphatic amines including mono-, di-, and triamines.These amines usually contain 1-8, and preferably 1-4, carbon atoms suchas methylamine, ethylamine, n-propylamine, n-butylamine, n-amylamine,n-hexylamine, ethylene diamine, diaminopropane, diaminobutane,pentamethylene diamine, diethylene triamine, and mixtures thereof.Particularly preferred amines in this group are the diamines having 2-4carbon atoms such as ethylene diamine.

b. The primary aromatic amines including mono-, di-, and triamines.Preferably these contain 6-8 carbon atoms such as aniline,methylaniline, phenylene diamine, toluene diamine and triaminobenzene. Aparticularly preferred amine in this group is toluene diamine which maybe any isomer, such as 2,3-, 2,4-, and 2,6-toluene diamine, or a mixtureof such isomers.

c. The alkanolamines, i.e., the aliphatic hydroxy amines. Usually eachalkanol group in these amines contains from 2 to 5 carbon atoms.Illustrative are ethanolamine, diethanolamine, triethanolamine, themono-, di-, and tripropanolamines, ethanolpropanolamine,diethanolpropanolamine, and the mono-, di-, and tributanolamines.Particularly preferred alkanolamines are those in which each alkanolgroup contains 2-3 carbon atoms such as the ethanolamines, thepropanolamines and the ethanolpropanolamines.

The most preferred amines referred to above are selected from the groupconsisting of ethylene diamine, diaminopropane, toluene diamine, anethanolamine such as mono-, di-, and triethanolamine, a propanolaminesuch as mono-, di-, and tripropanolamine, an ethanolpropanolamine suchas monoethanolmonopropanolamine and diethanolpropanolamine, and mixturesof these amines.

Any suitable alkylene oxide, or a mixture of alkylene oxides, may beemployed in the process of the present invention. However, it ispreferable to utilize a lower alkylene oxide having between 2 and about6 carbon atoms, such as ethylene oxide or propylene oxide or a mixturethereof.

A variety of conventional oxyalkylating catalysts may be used incarrying out the oxyalkylation reaction. However, it is preferred toemploy an alkaline catalyst such as potassium hydroxide. Theoxyalkylation reaction is allowed to proceed, usually using elevatedtemperatures, until a polyol product is obtained which has a hydroxylnumber of about 30 to about 800, and preferably about 250 to about 600.The use of elevated temperatures and basic catalysts is conventional inthe oxyalkylation art. Proper use of these should be apparent to thoseskilled in the art. The catalyst is generally employed in an amount ofabout 1 to about 5 percent by weight of the polyol. The oxyalkylationreaction is initially exothermic and cooling means are employed in orderto maintain the reaction at the desired temperature.

In general, after completion of the oxyalkylation reaction, the basiccatalyst is neutralized with a mineral acid, such as phosphoric acid,sulfuric acid or hydrochloric acid. The resultant polyol product is thenrecovered.

Either the so-called "one-shot method" or the "semiprepolymer technique"("quasiprepolymer technique") may be employed in preparing polyurethanefoams from the starch-amine-based polyols.

Any organic polyisocyanate may be employed in the preparation of thepolyurethane foams, including diisocyanates, triisocyanates, andpolyisocyanates. Organic diisocyanates are preferred due to commercialavailablity, especially mixtures of isomers of toluene diisocyanatewhich are readily available commercially, such as the 4:1 mixture of the2,4- and 2,6-isomers. Typical exemplificative isocyanates include, butare not limited to, the following: methylene-bis-(4-phenyl isocyanate),3,3'-bitolylene-4,4'-diisocyanate, 3,3'-dimethoxy-4,4'-biphenylenediisocyanate, naphthalene-1,4-diisocyanate, hexamethylene, diisocyanate,1,4-phenylene diisocyanate, polymethylene polyisocyanate (such as may bepurchased commercially under the trademark "PAPI"), etc., and mixturesthereof. The amount of isocyanate employed in the preparation of thepolyurethane foams should be sufficient to provide at least about 0.7NCO groups based on the number of hydroxyl groups present in thestarch-amine-based polyether polyol of the present invention, the numberof hydroxyl groups in any additive employed and the number of hydroxylgroups employed in the blowing agent. An excess of isocyanate compoundmay be conveniently employed; and it is preferable, therefore, to employabout 1.0-1.25 NCO groups based on the number of hydroxyl groups.

The polyurethane foams are prepared in the presence of a foaming agentand a reaction catalyst. The foaming agent employed may be any of thoseknown to be useful for this purpose, such as water, the halogenatedhydrocarbons and mixtures thereof. Typical halogenated hydrocarbonsinclude, but are not limited to, the following:monofluorotrichloromethane, difluorodichloromethane,1,1,2-trichloro-1,2,2-trifluoroethane, methylene chloride, chloroform,carbon tetrachloride, and mixtures thereof. The amount of blowing agentemployed may be varied within a wide range. Generally, however, thehalogenated hydrocarbons are employed in an amount from 1 to 50 parts byweight per 100 parts by weight of the starch-amine-based polyetherpolyol of the present invention, and generally the water is employed inan amount of from 0.1 to 10 parts by weight per 100 parts by weight ofthe starch-amine-based polyether polyol of the present invention.

The polyurethane foams are prepared in the presence of a catalyticamount of a reaction catalyst. The catalyst employed may be any of thecatalysts known to be useful for this purpose, including tertiary aminesand metallic salts. Typical tertiary amines include, but are not limitedto, the following: N-methyl morpholine, N-hydroxyethyl morpholine,dimethylcyclohexylamine, triethylene diamine, triethylamine,trimethylamine and mixtures thereof. Typical metallic salts include, forexample, the salts of antimony, tin and iron, e.g., dibutyltindilaurate, stannous octoate, etc., and mixtures thereof. Generallyspeaking, the catalyst is employed in an amount from 0.1 to 5 percent byweight based on th starch-amine-based polyether polyol of the presentinvention.

The polyurethane foams of the present invention may be prepared directlyfrom the reaction between the starch-amine-based polyether polyol andorganic polyisocyanate in the presence of a foaming agent and a reactioncatalyst. Optionally, various additives may be employed in thepreparation of the polyurethane foams in order to achieve particularproperties. Exemplificative of such additives include, but are notlimited to, the following: halogen and phosphorus-containing reactiveand non-reactive type additives to improve flame retardancy,monocarboxylic and polycarboxylic acid-based polyesters, monohydroxycompounds, polyhydroxy compounds, etc.

Some of the starch-amine-based polyols employed in the present inventionare characterized by a high room temperature viscosity. In these casesin order to prepare the polyurethane foam it will be necessary to applyheat in order to reduce the viscosity or to admix therewith a material,such as a polyether polyol, of lower viscosity. This may be convenientlyaccomplished by admixing a lower viscosity starch-amine-based polyolwith the higher viscosity starch-amine-based polyol.

It is preferred in the preparation of the polyurethane compounds of thepresent invention to employ minor amounts of a surfactant in order toimprove the cell structure of the polyurethane foam. Typical of suchsurfactants are the silicone oils and soaps. Generally up to 2 parts byweight of the surfactant is employed per 100 parts of starch-amine-basedpolyether polyol.

Various additives can be employed which serve to provide differentproperties, e.g., fillers, such as clay, calcium sulfate, or ammoniumphosphate may be added to lower cost and improve physical properties.Ingredients such as dyes may be added for color, and fibrous glass,asbestos, or synthetic fibers may be added for strength. In addition,plasticizers, deodorants and anti-oxidants may be added.

The process of the invention provides a relatively simple andpractically attractive route to preparing starch-amine-based polyetherpolyols. Furthermore, these polyols can be used in making rigidpolyurethane foams having highly satisfactory physical properties. Theseobjectives are achieved at minimum cost and without, at the same time,undermining the physical properties of the resulting polyols or of thepolyurethane foams prepared therefrom.

The process of the present invention will be more readily apparent froma consideration of the following illustrative examples. In the followingexamples the starch employed contained associated therewith about 10 to15 percent by weight of water. All parts and percentages are by weightunless indicated otherwise.

EXAMPLES 1 AND 2

The hereinbelow outlined general procedure was followed in thepreparation of starch-amine-based polyols. The specific formulations areset forth in Table I below.

A 2-gallon, stainless steel reactor was charged with the diethyleneglycol and the sulfuric acid. The mixture was heated to 115°-125° C. andthe starch was added to the mixture at a rate such as to maintain thetemperature between 110°-125° C. The temperature was maintained at125°-130° C. until the starch was completely dissolved in the reactionmixture. The mixture at that stage is dark in color and bright inappearance.

Approximately 1.0-1.5 hours were required for hydrolysis of the starch.0.06 Mole of potassium hydroxide was charged into the reaction mixture.The diethanolamine was then added to the mixture and during the additionthe temperature was decreased to 100°-110° C. Keeping the temperature at100°-105° C., excess water was separated so that the water concentrationwas a maximum of 1.0 percent by weight of the mixture. The temperaturewas raised to 110°-112° C. and maintained in the range while thealkylene oxide was added. After addition of the alkylene oxide, heatingwas continued for 30 minutes maintaining the temperature at 110°-112° C.before filtration of the product.

Analysis of the product gave the properties indicated in Table II.

EXAMPLE 3

The hereinbelow outlined general procedure was followed in thepreparation of a starch-amine-based polyol. The specific formulation isset forth in Table I below.

A 2-gallon, stainless steel reactor was charged with the diethyleneglycol and the sulfuric acid. The mixture was heated to 115°-125° C. andthe starch was added to the mixture at a rate such as to maintain thetemperature between 110°-125° C. The temperature was maintained at125°-130° C. until the starch was completely dissolved in the reactionmixture. The mixture at that stage is dark in color and bright inappearance.

Approximately 1.0-1.5 hours were required for hydrolysis of the starch.0.06 Mole of potassium hydroxide was charged into the reaction mixture.The diethanolamine was then added to the mixture and during the additionthe temperature was decreased to 110°-112° C. Water was condensed.Keeping the temperature at 110°-112° C., and without separating thewater, alkylene oxide was added. After addition of the alkylene oxide,heating was continued for 30 minutes maintaining the temperature at110°-112° before filtration of the product.

Analysis of the product gave the properties indicated in Table II.

                  TABLE I                                                         ______________________________________                                        Component     Example                                                         (Moles)       1          2        3                                           ______________________________________                                        Starch.H.sub.2 O                                                                            2.0        2.0      2.0                                         Diethylene Glycol                                                                           1.0        1.0      1.0                                         Sulfuric Acid 0.025      0.025    0.025                                       Diethanolamine                                                                              2.25       3.56     2.25                                        Propylene Oxide                                                                             15.4       14.87    22.10                                       Ethylene Oxide                                                                              --         7.02     --                                          ______________________________________                                    

                  TABLE II                                                        ______________________________________                                                    Example                                                           Property      1          2        3                                           ______________________________________                                        Hydroxyl Number                                                                             530        502      529                                         Nitrogen, percent                                                                           1.86       2.40     1.58                                        ______________________________________                                    

EXAMPLE 4

A rigid polyurethane foam was prepared from the product of Example 1 byadmixing the following ingredients in the following proportions:

    ______________________________________                                                                  Amount                                              Ingredient                (Grams)                                             ______________________________________                                        Liquid Product of Example 1                                                                             100                                                 Dow Corning® 191 surfactant.sup.1                                                                   2                                                   Dimethylcyclohexylamine catalyst.sup.2                                                                  4                                                   Trichloromonofluoromethane blowing agent.sup.3                                                          37.4                                                Polymethylene polyphenylisocyanate.sup.4                                                                145                                                 ______________________________________                                         .sup.1 This is a siliconeglycol copolymer described in 1977 Dow Corning       bulletin, No. 22476-77.                                                       .sup.2 This is a commercial product of Abbott Laboratories purchased unde     the trademark "Polycat8".                                                     .sup.3 This is a commercial product of E. I. DuPont de Nemours and Compan     purchased under the trademark "R11 B".                                        .sup.4 This is a commercial product of Upjohn Company purchased under the     trademark "PAPI135" and having an approximate functionality of 2.6.      

The mixture was allowed to foam and was cured at elevated temperatures.The resultant rigid polyurethane foam had the physical properties listedin Table III.

EXAMPLES 5 AND 6

In the following Examples, the procedure of Example 4 was repeatedexcept that the products of Examples 2 and 3 were used in Examples 5 and6, respectively. The resultant rigid polyurethane foam had the physicalproperties listed in Table III.

                  TABLE III                                                       ______________________________________                                                          Example                                                                       4     5        6                                            ______________________________________                                        Liquid Product, Example                                                                           1       2        3                                        Cream, sec.         16      8        12                                       Gel, sec.           49      24       48                                       T. Free, sec.       76      38       68                                       Rise, sec.          103     56       92                                       Density, p.c.f.     1.95    1.84     2.03                                     Compressive Strength, p.s.i.                                                                      41.80   42.10    30.65                                    Compressive Strength, p.s.i.                                                                      20.90   17.00    17.90                                    C-Factor            0.118   0.119    --                                       K-Factor            --      --       0.142                                    Friability          8.22    3.07     3.27                                     Porosity            85.09   85.12    78.74                                    Dry Heat Age, @ 200° F.                                                                    4.22    6.20     5.13                                     Dry Heat Age, @ 230° F.                                                                    13.99   12.52    13.50                                    Humid Age, @ 158° F./100% RH                                                               11.59   13.46    10.34                                    ______________________________________                                    

What is claimed is:
 1. In a polyurethane foam comprised of the reactionproduct of a polyol reactant, an organic polyisocyanate reactant, areaction catalyst and a foaming agent, the improvement wherein saidpolyol reactant is prepared by:a. forming a crude polyglucoside reactionproduct by reacting in the presence of a catalytic proportion of an acidcatalyst,(1) starch and (2) a polyhydric alcohol containing at least twohydroxyl groups, the proportion of said alcohol being at least 0.3 moleof alcohol per glucose unit weight of starch, and b. admixing said crudepolyglucoside reaction product with an amine in the presence of a basiccatalyst, maintaining said mixture at a temperature of from 100° to 165°C., and introducing into said mixture an alkylene oxide having between 2and about 6 carbon atoms, said amine being employed in an amount of atleast about 0.1 mole to about 10 moles per glucose unit weight of starchand being selected from the group consisting of an aliphatic aminehaving 1-8 carbon atoms, an aromatic primary amine having 6-8 carbonatoms, an alkanolamine in which each alkanol group contains 2-5 carbonatoms, and a mixture thereof.
 2. The polyurethane foam of claim 1,wherein said starch is corn starch.
 3. The polyurethane foam of claim 1,wherein said acid catalyst is sulfuric acid.
 4. The polyurethane foam ofclaim 1, wherein said alkylene oxide is propylene oxide.
 5. Thepolyurethane foam of claim 1, wherein said alkylene oxide is a mixtureof propylene oxide and ethylene oxide.
 6. The polyurethane foam of claim1, wherein said aliphatic amine is a diamine having 2-4 carbon atoms,said aromatic amine is toluene diamine, and said alkanolamine is anethanolamine, a propanolamine or an ethanolpropanolamine.
 7. Thepolyurethane foam of claim 1, wherein said amine is selected from thegroup consisting of ethylene diamine, toluene diamine, an ethanolamine,and a mixture thereof.
 8. The polyurethane foam of claim 1, whereinwater is separated from said crude polyglucoside reaction product priorto reaction with said alkylene oxide.
 9. The polyurethane foam of claim1, wherein said amine is an ethanolamine.
 10. The process of claim 9,wherein said starch is corn starch.
 11. The process of claim 10, whereinsaid acid catalyst is sulfuric acid.
 12. The process of claim 11,wherein said alkylene oxide is propylene oxide.
 13. The process of claim11, wherein said alkylene oxide is a mixture of propylene oxide andethylene oxide.